Heater for fluids



INVENTOR FIG.3

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caLAz c July 4, 1950 Patented July 4, 1950 UNITED STATES PATENT OFFICE HEATER FOB FLUIDS Emil F. Gleber, St. Albans, N. Y., assignor to The M. W. Kellogg Company, Jersey City, N. 1., a corporation of Delaware Application October 29, 1941, Serial No. 782,715

4 Claims. (c1. res-ass) This invention relates in general to furnaces for heating fluids and is particularly applicable to vertical type furnaces provided with a series of vertical wall tubes extending through both a radiant heating section at thebottom and a convection heating section at the top, and being connected to form a continuous flow path for the fluid to be heated.

Furnaces of this general type have found wide application in the petroleum refining and chemical processing arts, comprising in their most common form a vertical cylindrical heating chamber having a heat source at the bottom and a flue at the top and an annular series of wall tubes provided at their upper ends with suitable extended surfaces for obtaining increased heat transfer efficiency in the upper portion of the heating chamber. The heating chamber is divided into a radiant heating section containing the bare portions of the tubes and a convection heating section containing the extended surface portions of the tubes. Various bame arrangements have heretofore been proposed for directing the flow of combustion gases from the radiant heating section into the connection heating section and along the extended surface portions of the tubes before discharging to the flue.

The present invention is particularly directed to improvements in the convection section of a vertical type furnace and has as its primary obiect the utilization to fullest advantage of extended surface tubing within the convection heating section. In connection with such use of extended surface tubing it has heretofore been proposed to construct the extended surfaces in the form of longitudinal fins attached, as by welding, to the outer surfaces of the tubes. Such longitudinal extended surfaces or flns, as they are commonly called, operate at maximum effl- I ciency when the flow of combustion gases over the external portions of the tubes is substantially parallel to the fin surfaces. It has been observed, however, that increased heat transfer efflciency may be obtained when the flow of the combustion gases is transverse with respect to the flow of the heat exchange medium within the tubes. This observation has led to the development of annular or helical finned tubes, and such tubes are generally accepted as preferable in such applications where the design characteristic of the apparatus will permit cross-flow of the external heat exchange medium with respect to the flow of fluid within the tubes.

It is an object of the present invention, therefore, to provide a fluid heating furnace embodying an elongated heating chamber comprising a radiant section at one end and a convection section at the other end and including a bank of tubes extending longitudinally through both sections provided with fins on the tube portions within the convection section, in which the combustion gases from -the radiant section are directed throughthe convection section in one or more paths substantially entirely in a direction transverse to the axes of the tubes.

A further object of the invention is to provide a low cost fluid heating furnace of compact design efllcient and economical in operation, and permitting ready access to the tubes and other internal portions of the furnace for the purposes of inspection, cleaning and repair.

These and other objects are effected by this invention, as will be apparent from the following description and claims taken in connection with the accompanying drawing forming a part of this application, in which:

Fig. 1 is a sectional view in elevation of a furnace constructed in accordance with the present invention;

Fig. 2 is a horizontal section taken along the line 2-1 of Fig. 1; and

Fig. 3 is an enlarged fragmentary section showing the expansion and sealing arrangement for the lower end of the baffle forming the constricted convection section, and the arrangement and construction of the fins on the heating tubes.

Referring to Fi 1 of the drawing, the structure illustrated is a vertical type furnace of generally conventional design, such as might be employed as a feed preheater in petroleum refining operations. While the invention is especially suited for use with the upright cylindrical form of heater illustrated, it is not so limited in its application, and in a proper case may readily be adapted for use in the convection section of other types of furnace.

The main body portion of the heater comprises a cylindrical shell ii provided with a refractory lining including an initial layer 12 of block insulation covered by a secondary layer l3 of circular fire brick. The lined shell, which forms the heating chamber of the furnace, is mounted in an upright elevated position on vertical supports it. A flat circular metal plate l5 closes the bottom of the shell and supports a refractory lining comprising a bottom layer of block insulation l6 and a top layer of fire brick admit a burner nozzle ll, through which a suitable fuel is supplied, from a source not shown, for combustion within the lower or radiant section 2| of the heating chamber.

A flat metal ring 2| is set on top of the refractory lined metal shell II to support an annular box girder 23 which, in turn, supports the lower conical end of a flue 24.

Tubes 25 are arranged in an annular row about the inner wall of the heating chamber, their lower ends terminating in conventional Y-flttings supported from the plate ll of the furnace floor and their upper ends projecting through openings in the bottom plate 26 of the annular box girder 2!. Suitable cross-overs or return bends are provided to connect the upper ends of the tubes in series arrangement, the cross-overs being situated outside of the heating chamber and within the box girder. The stems of the Y-flttings project through the furnace floor so that access to the clean-out plugs may be had externally of the heating chamber. The top plate 21 of the box girder is removable, to provide ready access to the ends of the tubes for the purpose of removal, inspection, or cleaning. A refractory lining 28 is provided for the inner side and bottom walls of the box girder 23. A suitable refractory lining 2! is also provided for the flue and the inner side surface of the box girder.

Within the heating chamber the upper portions of the tubes 25 are provided with a series of longitudinally spaced transverse flns 3|, which may be in the form of separate annular rings or turns of a continuous helix. The finned area of the tube bank extends downwardly from the top of the heating chamber a distance suflicient to provide the correct balance between the convection heated portion of the tubes and the radiant heated portion.

A cylindrical baflle of heat resistant alloy. generally indicated by the numeral s2, is concentrically positioned within the upper end of the heating chamber to constrict the chamber and to provide a relatively narrow annular passage or convection zone 33 through which the not combustion gases discharging from the radiant section 2| of the heating chamber are passed to the flue 24. The convection passage 3! contains only the flnned portions of the tubes, so positioned that the hot combustion gases may flow freely between and around the tubes. The baiiie 32 comprises a cylindrical member 34 attached to and depending from the inner edge Of bottom plate 2' of the box girder 23. The lower edge of cylindrical member 34 is provided with an outwardly extending horizontal flange 3| having a series of perforations to receive the tubes 25. The outer edge of flange member 35 is provided with a downwardly extending vertical flange I which overhangs and overlaps an upwardly extending flange I'l formed along the inner edge of a flat annular seal ring 32 partially set in the refractory brick portion It of the furnace wall. The flanged ring II is supported from the shell II by means of a circumferential row of support members a, which may be in the form of radially extending bars attached at one end, as by welding, to the inner wall of the shell.

The horizontal flange 35 of baiiie 32 and the seal ring it are spaced a vertical distance greater than the width of the overlapping vertical flanges I and 31, so that the baiile 32 is free to expand or contract longitudinally in accordance with temperature conditions within the furnace while at the same time maintaining an effective seal against the admission of combustion gases from the radiant section into the convection section at this point. Cylindrical member 34 is provided with full-length vertical partitions 4| extending centrally across the opening, Joined along their vertical edges to the walls of the cylinder 34, thus dividing the hollow cylinder 34 into three separate sections or zones. The outer zones 42 and 43 are closed at the upper end by segmental members 44 and 45, respectively, and the central zone 48 is closed at its lower end by closure member 41. The hollow zones 42 and 43, therefore, are in open communication with the radiant section 2| of the heating chamber, and the hollow zone 46 is in open communication with the flue 24. To provide reinforcement for the vertical partitions 4|, one or more stiffener members 4! may be provided.

At opposite sides of the zone 4. a vertical slot 49 is provided in the walls of cylindrical member 34 to provide open communication between the zone 48 and the annular convection section 33. The slots 4! extend substantially the entire length of the cylinder 24. A pair of diametrically opposite vertical slots 5| are provided in the side walls of the cylinder 34 ninety degrees removed from the slots 49 to provide open communication between the segmental zones 42 and 43 and the annular convection section 33.

The hot combustion gases rising from the radiant section 2| pass into the zones 42 and 43 and are deflected radially outward through the vertical slots or ports 5|. The portions of the tubes 25 directly opposite the openings 5| may be left bare depending upon whether or not the temperatures within the zones 42 and 48 are sufllciently high to cause burning of the fins on the tube. As clearly shown in Fig. 2, the gases entering the annular convection section through the ports 5| divide into two streams which travel in opposite directions along the annular convection passage. These separate streams of combustion gases traverse a fourth of the annular convection passage and are Joined by combustion gas streams from the opposite port 5| traveling in the opposite direction. Together they pass through the vertical slots or ports 49 into the zone 44, from which zone they are discharged upwardly to the flue 24. This arrangement permits true cross-flow of the hot combustion gases over the finned portions of the tubes 25 within the convection section 33, so that a maximum heat transfer coeflicient is obtained.

Although the embodiment of the invention iilustrated in the drawing shows a baille arrangement whereby the combustion gases are passed through the convection passage in four separate streams, each stream contacting approximately one-fourth of the total flnned tube surface, it is obvious that fewer or more passages may be provided by suitably partitioning the baflle 32 to provide the desired number of hollow zones.

Furthermore, the invention is not limited to the cylindrical type of heating chamber illustrated, but is applicable to furnaces of rectangular or other cross-section. It will be apparent to those skilled in the art that various other changes and modifications may be made within the spirit of this invention, and it is desired, therefore, that only such limitations shall be placed thereon as are imposed by the appended claims.

What is claimed is:

1. In a vertical type radiant-convection fluid heater including a cylindrical heating chamber and an annular row of full-length wall tubes having transverse fins at their upper ends, the combination with said chamber of a baflle comprising a hollow cylindrical member concentrically positioned in the upper convection portion of said heating chamber to provide a narrow annular convection passage containing the finned portions of said tubes, means attached to the lower end of said cylinder and to the inner wall of said heating chamber to provide an expandible joint efiectively sealing the bottom of said annular convection passage against the admission of radiant energy and hot combustion gases directly from the radiant section, partitioning means for sub-dividing the space within said cylindrical member to provide one or more zones in open communication with the radiant section of said heating chamber and one or more other zones in open communication with the flue end of said heating chamber, said first and second zones being in open communication with said annular convection passage through openings provided therefor and spaced at intervals in said hollow cylindrical member.

2. In a vertical type radiant-convection fluid heater including a cylindrical heating chamber and an annular row of full-length wall tubes having transverse fins at their upper ends, the. combination with said chamber of a bafiie comprising a hollow cylindrical member concentrically positioned in the upper portion of said heating chamber and extending longitudinally to a point below the lowermost of said fins, a flange on the lower end of said cylindrical member extending radially outward to a point beyond said row of wall tubes and having perforations to receive the latter, an annular seal ring attached to the inner wall of said heating chamber and extending radially inward to a point within the outer edge of said flange, said seal ring and said flange being interlocked to provide a substantially fluid-tight expandible joint, a pair of substantially vertical partitions extending centrally across the space within said cylinder and attached along their edges tothe cylinder walls, said partitions dividing the cylinder into three separate zones, closure members for the upper ends of the outer of said zones, a closure member for the lower end of the intermediate of said zones, and ports in the walls of said cylinder providing communication between said outer zones and said convection passage and between said intermediate zone and said convection passage.

3. A fluid heater as in claim 2 in which said ports are arranged to provide circumferential paths of equal length within said annular convection passage.

4. A flue gas bafiling system for the convection section of a vertical type fluid heater having a cylindrical heating chamber and full-length wall tubes extending through both the radiant and the convection sections comprising a hollow cylindrical member concentrically positioned within the upper convection portion of said chamber to provide a narrow annular convection passage, annular shielding means for shielding the bottom of said annular convection passage against the ad-- mission of radiant energy and hot combustion gases from the radiant section of said chamber, means for partitioning the space within said cylinder to provide a plurality of separate zones, ports along the walls of said cylinder providing communication between said annular convection passage and each of said zones, closure members at the lower ends of one or more of said zones, and closure members at the upper ends of th remaining of said zones.

EMIL F. GLEBER.

REFERENCES CITED UNITED STATES PATENTS Name Date Huflf Oct. 4', 1932 Number 

